docs(readme): add description of repository maintenance status

[34j]

Description of change

copilot:all

Pull-Request Checklist

• Code is up-to-date with the main branch
• This pull request follows Contributing.md
• This pull request links relevant issues as Fixes #0000
• pre-commit run -a passes with this change or ci passes
• poetry run pytest passes with this change or ci passes
• (There are new or updated unit tests validating the change)
• Documentation has been updated to reflect this change
• The new commits follow conventions outlined in the conventional commit spec

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 19.25%. Comparing base (b7639ca) to head (4844ff2).
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1143   +/-   ##
=======================================
  Coverage   19.25%   19.25%           
=======================================
  Files          39       39           
  Lines        3496     3496           
  Branches      497      497           
=======================================
  Hits          673      673           
  Misses       2804     2804           
  Partials       19       19           

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